In the past few years enormous advances have been made in lightwave technology providing multichannel transmission over optical fibers. Coherent optical frequency multiplexing communication techniques are a promising way to supply multichannel high capacity communication services. Making use of its high sensitivity, coherent techniques are today on the way to the deployment in the field for point to point connections, e.g., Ref. 1. Additionally using the high selectivity of this technique, coherent multicarrier techniques (CMC) were investigated for point to multipoint connections such as TV distribution systems in many laboratories, and very impressive results were achieved, e.g. Refs. 2-5. Even for this, CMC systems are on the way to first field trials. The implementation of CMC techniques in communication systems is investigated today to use the capacity of CMC techniques even in bidirectional and switching systems.